Soil moisture conditions across the three counties vary from normal to moderate drought.
Soybeans planted in April are in the R5 stage (Full Pod), and the April-planted corn is in the R4 stage (Dough), with ear tip kernels starting to dent.

Over the past two weeks, heavy rains have fallen in some areas, and Red Crown Rot is beginning to appear where those high rainfalls occurred. If you suspect Red Crown Rot, send a plant sample to the University of Illinois Plant Clinic for positive identification.

Remember, interveinal chlorosis of soybean leaves can be caused by Brown Stem Rot, Sudden Death Syndrome, or Red Crown Rot.

A week without precipitation, and northeast Illinois returns to abnormally dry on the U.S. Drought Monitor. Disease pressure in corn is starting to build as much of the crop has reached R4 (dough stage). A Corn Fungicide ROI Calculator tool—accessible on the Crop Protection Network website—is designed for both gray leaf spot and tar spot when corn is in the V10 to R3 growth stages. It requires inputs for expected yield, marketing price, and either a low or high disease estimate. Using those inputs, the tool provides a breakeven probability for most commonly used fungicides. Iowa State suggests that, regardless of which fungal diseases are present, a fungicide application after R3 is not likely to provide a return on investment.

This week I traveled to campus for the Illinois FFA Crop Scouting Competition. A windshield survey of the 90-mile trip on backroads from Champaign north to Grundy County suggests, once again, some remarkable corn and soybean crops in this region of the state.

We had a few corn leaf aphid reports, but nothing approaching what we saw last year; those should be winding down as most of the crop progresses well into the reproductive stages. I’ve received several identification requests for the redheaded flea beetle, so I thought I would share a photo. These have been easy to find this year in both corn and soybeans; every few years, we see abnormally high numbers. As you can see from the picture, they resemble the corn flea beetle (the vector of Stewart’s wilt), but they are much larger—maybe 3/16″ to 1/4″ long—and have a reddish-brown head, as the name suggests. While they will feed on corn and soybean foliage and can be found quite easily in corn silks, I’ve never seen them approach economically damaging levels.

In my field survey this week, most of the soybeans staged anywhere from mid- to late R3 to mid R5. Fields seem to have done well setting pods, though I was not seeing many four-bean pods at this point. Corn was staging from mid- to late blister (R2) through late milk (R3). Developing ears are beginning to reach a respectable size, and the silks are browning and drying in the fields that are farther along.

We are getting a reprieve from some of the heat we experienced over the last couple of weeks, with daytime highs in the mid to upper 80s and overnight lows now forecast to be in the upper 60s to low 70s. We even had a few nights dip into the upper 50s. These comfortable overnight temperatures provide the crops with a much-needed break from the heat and sunshine during the day, allowing them to fill ears and pods at a better pace—hopefully improving test weight.

Both corn and soybean crops look great right now, with plentiful moisture from rains throughout most of July. This is keeping the crop green and mostly healthy, with the exception of corn leaf diseases coming in and an array of soybean feeders as well. I believe that growers who decided to spray fungicides this season will be happy with that choice. I worry about fields that were not sprayed. Unfortunately, I also see enough disease coming back in now that a second application may become necessary due to increasing tar spot and other diseases. Our saving grace will be that the corn crop is maturing at a rapid pace.

I focused this week’s crop report on the double-crop soybeans during my travels to southern Illinois, where my parents live. Due to a wet June and early July, the soybeans planted after wheat went in under less-than-ideal conditions. Most of the fields I walked or drove by are around 80–85% emerged. This made weed control tougher, and yields will likely be below average due to only 80–85% of the plants emerging in these fields. Waterhemp is a main issue in all soybeans. Early rainfall did not allow pre-emerge herbicides to do their job, and some fields unfortunately were not sprayed and relied solely on a post-emergence application. Even with these weed issues, overall the soybeans and corn crop look really good for southwest Illinois this time of year.